RELATED PARTY TRANSACTIONS - Narrative (Details)	1 Months Ended	12 Months Ended
	May 31, 2019 USD ($)	Dec. 31, 2019 USD ($) quarter	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Related Party Transaction [Line Items]
Management fee renewal term		1 year
Incentive fees incurred		24 months
Carrying Amount		$ 1,682,498,000	$ 1,524,873,000
Outstanding principal		$ 1,692,894,000	1,534,743,000
Affiliated Entity
Related Party Transaction [Line Items]
Base management fees as a percentage of stockholders' equity per annum		1.50%
Incentive fee payable		$ 0
Percentage multiplied to arrive at first value affecting calculation of incentive fees		20.00%
Previous period for which core earnings are considered to arrive at first value affecting calculation of incentive fees		12 months
Previous period for product of weighted average price per share and weighted average number of shares of common stock and other shares		12 months
Percentage multiplied to arrive at difference of first value affecting calculation of incentive fees		8.00%
Period whose fiscal quarters are considered to arrive at first value affecting calculation of incentive fees		12 months
Minimum cumulative core earnings, number of quarters | quarter		12
Minimum cumulative core earnings		$ 0
Revenue from Related Parties		1,100,000	1,200,000	$ 381,000
Residential
Related Party Transaction [Line Items]
Carrying Amount		$ 40,900,000	$ 34,000,000
Loan Purchase Commitments | NORTH CAROLINA | Senior Mortgage Loans | Industrial
Related Party Transaction [Line Items]
Loan purchased from affiliate	$ 40,500,000
Outstanding principal	$ 34,900,000